1. Field of the Invention
The present invention relates to an electron emission device, its fabrication method, and an electron emission display including the electron emission device.
2. Discussion of Related Art
Generally, an electron emission device is classified as either a hot cathode type or a cold cathode type, wherein the hot cathode type and the cold cathode type employ a hot cathode and cold cathode as an electron emission source. A cold cathode type electron emission device comprises a structure, such as a Field Emitter Array (FEA), a Surface Conduction Emitter (SCE), a Metal Insulating Layer Metal (MIM), a Metal Insulating Layer Semiconductor (MIS), and a Ballistic Electron Surface Emitter (BSE).
The foregoing electron emission devices are employed for an electron emission display, backlighting, and a lithography electron beam. Among these, the electron emission display comprises an electron emission region provided with the electron emission device to emit electrons, and an image-displaying region in which the emitted electrons collide with a fluorescent material to emit light. Generally, the electron emission display comprises a plurality of electron emission devices formed on a first substrate; a driving electrode to control the electron emission of electron emission devices; a fluorescent layer formed on a second substrate and colliding with the electrons emitted by the first substrate; and a focusing electrode to accelerate the electrons towards the fluorescent layer.
In a triode electron emission display comprising a cathode electrode, an anode electrode and a gate electrode, a predetermined driving voltage is applied between the cathode electrode and the gate electrode, and a voltage difference therebetween creates an electric field, thereby causing an electron emission device to emit electrons and to accelerate the electrons towards a fluorescent layer. Such an electron emission display has a high brightness and a wide viewing angle like that of a Cathode Ray Tube (CRT) display.
In such an electron emission device, the electron emission region is formed on the cathode electrode by a thick film process or a thin film process. In a thick film process, a film material is squeezed out through a mesh aperture of a mesh mask by a squeezer or a rubber roller, thereby printing the electron emission region. In the thick film process, there are problems in that the electron emission region is not accurately aligned and the height of the printing pattern is irregular, thereby short circuiting the gate electrodes due to the reduced accuracy.
To solve the above-described problems, a method of fabricating an electron emission device is discussed in Korean Patent First Publication No. 2003-28244. Hereinbelow, a method of fabricating an electron emission device will be described by way of example.
This method applies an exposure technology to the thick film method, so that the electron emission regions can have regular height without the thin film method.
In a method of fabricating an electron emission device, a transparent Indium Tin Oxide (ITO) electrode is formed on a substrate. A stripe electrode having a constant conductivity is formed in the transparent electrode. Then, a dielectric layer is formed on the substrate having the stripe electrode. Then, a gate electrode is formed on the dielectric layer. Thereafter, an aperture formed on the substrate by the transparent electrode, the stripe electrode and the dielectric layer is filled with a photosensitive material, e.g., a Carbon Nano Tube (CNT) paste, and then processed by a rear exposure process. After the rear exposure, the photosensitive material is developed and dried, thereby forming an electron emission region.
The rear exposure process is used in the method of fabricating the electron emission device noted above, so that the ITO electrode is employed. However, the electrode resistance of the ITO electrode is relatively high, for instance, the electrode resistance of the ITO electrode is about 100KO in the case of the electron emission device of 38 inches. Therefore, in such an electron emission device having the top-gate structure, a relatively high voltage must be supplied to the cathode electrode employed as the data electrode. To supply the high voltage to the cathode electrode, the cross section of the cathode electrode must be large. As the cross section of the cathode electrode becomes larger, the breakdown voltage of the dielectric layer must be increased, and therefore the thickness of the dielectric layer must also be increased. In addition to the problem, the higher the voltage supplied to the cathode electrode, the more power the electron emission display consumes.
Furthermore, the rear exposure process is used in the method of fabricating the cathode substrate of the electron emission display, so that an expensive glass substrate such as a PD200 ITO glass must be employed. Since the expensive glass substrate must be employed, there arises a problem in that the production cost of the electron emission display is increased.
Korean Patent Publication Nos. 10-1997-0051793, 10-1997-0030078, and 2003-234062 each relate to methods of manufacturing field emission devices bearing features in common with the present invention. However, none of these references teach or suggest the all of the features of the present invention recited in the appended claims.